Appearance-based evaluation of varnish removal methods in gilded surfaces

Abstract

This paper outlines the use of bidirectional reflectance measurements for the characterisation and evaluation of appearance changes in gilded surfaces caused by varnishing and cleaning. Oil and water gilding mock-ups representative of a 15th-century panel painting were varnished, and a selection of four varnish removal methods was applied. By measuring the bidirectional reflectance of the samples, their appearance was modelled and evaluated according to perceptual gloss attributes. Three main perceptual groups were found for each gilding type: unvarnished, varnished and cleaned surfaces. Finally, for the studied samples, the most appropriate method for removing dammar and colophony varnish from a gilded surface, in terms of appearance change, is solubilisation by applying an Evolon®CR compress.